In an image forming apparatus, a photosensitive drum is charged, the photosensitive drum is irradiated with light corresponding to printing image data (print data), and thus, a latent image (electrostatic latent image) is formed on the photosensitive drum. In the image forming apparatus, toner (developing agent) is attached from a developer to the latent image formed on the photosensitive drum, the toner attached to the latent image is transferred to a printing medium, and thus, a toner image is formed on the printing medium. In the image forming apparatus, the printing medium on which the toner image is formed is interposed between fixing rollers heated by a heater, and the toner image formed on the printing medium is fixed. There is an image forming apparatus in which toner is supplied from a toner cartridge to a developer.
There is an image forming apparatus in which a toner cartridge does not include a residual amount measurement sensor for measuring a residual amount of toner inside the toner cartridge. In this case, in the image forming apparatus, based on a driving time of a motor which drives a screw for supplying the toner from the toner cartridge to the developer, the number of pixels counted by a pixel counter, or the like, the residual amount of the toner inside the toner cartridge is estimated. In the image forming apparatus, based on the estimated toner residual amount, the toner cartridge being nearly empty is displayed on a display unit of the image forming apparatus.
However, an inertia rotation of the screw occurs even after the motor stops, and thus, a large deviation between an actual toner supply amount and the estimated toner residual amount may occur.